Well the Nvidia inspector way of tweaking is not an option for atm, as it means loosing the settings for FSX.
I did like the idea of getting Rex to work, as that would mean a major improvement of the cloud textures.
So far I am not seeing a reason to tweak the cfg file, as I am getting 60 - 100+ fps (which doesn't say that much). For me a smooth running sim is what it is all about, and I have no issues in that field with all settings to Ultra High.
Besides the already several times reported graphics issue, the sim itself is running very nice,